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I Metalli alcalini in sintesi organica: attivazione e selettività del sodio metallico in reazioni di metallazione riduttiva
Full text linkThis work mainly report the results obtained in the application of a new methodology , in organic
synthesis, mediated by alkali metals, especially sodium metal. The reaction of 1,2-diarylethenes
with Na metal in dry THF allows the generation of a wide array of 1,2-diaryl-1,2-disodioethanes,
and we showed that these vic-diorganometallics are very effective reductive elimination reagents,
useful in several applications. We investigated the reductive dehalogenation of several vicdisubstituted
compounds, and halogenated aromatic compounds. Our procedure is tolerant of
several functional groups, and shows promising applications as a new and selective protocol to be
employed in the reductive removal of protecting groups. We can say that 1,2-diaryl-1,2-
disodioethanes can be considered as synthetic equivalents of an activated, selective, and highly
reactive form of Na metal, functioning under homogeneous reaction conditions. Finally, following
our interest in the generation of polar organometallic reagents by the reductive cleavage of aromatic
and benzylic ethers as well as the employment of the resulting carbanions in the synthesis of
biologically active compounds, we investigated the effect of different alkali metals, namely Na and
Li, on the reductive metalation of 3,4,5-trimethoxybenzyl methyl ether, Indeed, this ether can be
considered as a cheap starting material allowing either the synthesis of 2,5-dialkylresorcinols, a
class of naturally occurring compounds endowed with cytotoxic and antibiotic activities, or of 1,2,3-
trimethoxyarenes, a class of compounds endowed, inter alia, with interesting anticancer properties
Active-alkali metal promoted reductive desulfurization of dibenzothiophene and its hindered analogues
Full text linkReductive desulfurisation of organic compounds is of importance both in organic synthesis and in industry. Benzo- and dibenzothiophenes are between the most abundant sulphur containing impurities in crude oils, and their desulfurization is a mandatory issue in the production of non polluting fuels. Following our interest in the development of efficient alkali metal-mediated synthetic procedures and alternative protocols for the chemical transformation of widespread environmental contaminants we wish to report here on the effectiveness of sodium and lithium metals, in the presence of catalytic amounts of tetraphenylethylene (TPE), in promoting the reductive
desulfurization of dibenzothiophene, as well as of the corresponding sulfone and sulfoxide
Reducing versus basic properties of 1,2-diaryl-1,2-disodioethanes
No full textThe outcome of the reaction between halogenated arylacetic acids and 1,2-diaryl-1,2-disodioethanes strongly depends on the nature of both reaction partners, and it can be rationalized in terms of a competition between reducing and basic properties of the vic-diorganometals, as well as of the ease of the reductive cleavage of the different carbon–halide bonds. As an application of these findings, we developed a particularly mild approach to the synthesis of halogenated and non halogenated α-substituted arylacetic acids
Metallazione riduttiva di 1,2-diarileteni: applicazioni sintetiche
Full text linkProseguendo nella nostra ricerca di nuove ed efficienti procedure basate sull’utilizzo di
metalli alcalini in sintesi organica, abbiamo studiato la reazione di metallazione riduttiva di
una serie di 1,2-diariletileni, e le possibili applicazioni sintetiche dei derivati vicdiorganometallici
così ottenuti
Riduzione regioselettiva del 3,4,5-trimetossibenzil metil etere: sintesi di resorcinoli 2,5-dialchilsostituiti
Full text linkVista l'esperienza maturata nel nostro laboratorio nella generazione di reattivi
organometallici di tipo benzilico e aromatico attraverso reazioni di metallazione riduttiva di
alchil benzil eteri, abbiamo ritenuto che il metil etere dell'alcool 3,4,5-trimetossibenzilico, fosse un substrato adatto alle nostre necessità sintetiche
Green and convenient arene-catalized reductive lithiation of heterocyclic compounds
Full text linkIn the last decades reductive lithiation established itself as a particularly powerful procedure for the generation of functionalized organometals. In addition, the enormous
role of this reaction in the reductive ring opening and functionalization of heterocycles has been reported. Accordingly, critical experiments were performed for the generation of lithium radical anions of several PAHs and a diene in both solvents, under both CA and SA protocols.
Almost all of the above mentioned hydrocarbons rapidly generate radical anions with different fascinating visible colors at 0 °C. Based on this, influence of different electron shuttles and their efficiency in the reductive lithiation of N-phenylaziridine, phthalan will be disclosed. Moreover, we will report an interesting example of chemoselectivity concerning to the reductive lithiation of 4-chlorobenzyl methyl ether in a green solvent
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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